1. Field of the Invention
This invention relates to lacrimal silicone tubes and a method of inserting the same, and more particularly, to lacrimal silicone tubes which are treated to reduce the friction between the tube and the supporting tissue.
2. Description of the Prior Art
Tears bathe the surface of the eye and then drain into puncta and canaliculi on the medial upper and lower lids. The tears flow from the canaliculi into the lacrimal sac down the nasolacrimal duct into the nose.
The nasolacrimal duct can become obstructed either congenitally or by an acquired obstruction in adulthood. When the nasolacrimal duct becomes obstructed, tears can no longer drain from the surface of the eye through the lacrimal system into the nose. The tears therefore well up over the eyes and spill over the lids onto the face and the patient has to constantly dab the eyes with a tissue. In addition, tears stagnate in the lacrimal sac which allows bacteria to multiply. The lacrimal sac then becomes infected (dacryocystitis). Dacryocystitis causes the lacrimal sac to become swollen, red, and painful. Pus exudes from the lacrimal sac through the canaliculi onto the eye and results in purulent material constantly covering the eye. In time, the dacryocystitis does not respond to antibiotics and surgery becomes necessary.
Dacryocystorhinostomy (DCR) is the surgery used to correct nasolacrimal duct obstruction. In a DCR a new opening (ostium) is created between the lacrimal sac and the nose. This allows tears to flow from the lacrimal sac through the DCR ostium into the nose. An open or incisional DCR requires an incision on the side of the nose. In an open DCR, a large DCR ostium is created by making a 17 mm, plus opening in mucosa and bone. This procedure has significant morbidity, a prolonged recovery, and the threat of scarring and hemorrhage. In contrast, a balloon DCR has much less morbidity, no incision, and a quick recovery. The balloon DCR ostium is smaller (5 mm.) Than that of an open DCR. Because the balloon DCR ostium is only 5 mm. in diameter, a stent is required to keep the DCR ostium open after surgery. Otherwise, postoperative inflammation and scarring may cause it to close.
A silicone tube is typically used to stent the ostium. The tube has metal probes at each end and may be inserted by pulling one probe and tube end through a punctum, a canaliculus, the lacrimal sac, and the ostium into the nasal cavity. The opposite end of the tube and its attached probe is then brought through the opposing punctum and canaliculus, the lacrimal sac, and the ostium into the nasal cavity. The probes are then grasped in the nasal cavity and brought down the nose and out the external naris, pulling the tube into position to stent the ostium, puncta, canaliculi and lacrimal sac. The tube is left in place as a stent for six months.
It has been found, however, that silicone tube stents induce lacrimal tissue reaction and inflammation. The inflammation lead, in time, to increased scar contraction around the ostium. Although this problem has existed for many years, no one has discovered the cause of this tissue reaction and inflammation, and no effective solutions have been suggested by the prior art.
Various balloon dilation catheters and methods using them are shown in U.S. Pat. No. 5,169,386. As stated at col. 3, lines 47-51, and col. 9, line 61, col. 10, line 2, it is desirable for the catheter to include a lubricous coating to facilitate insertion of the catheter into the lacrimal system. The coating may be a silicone coating bonded to the catheter or may be a topical coating of silicone oil. It is also suggested at col. 13, lines 62-65, that the necks of the balloon be plasma etched. The patent discusses prior art use of a silicone tube stent in an attempt to maintain patency of the ostium (col. 1, lines 61-64) and prior art use of a balloon catheter as a stent with the inflated balloon used to retain the stent in place (col. 2, lines 4-13).
The prior art teaches that stents used for other purposes can be coated. Medi-tech Boston Scientific Corporation sells ureteral stents which are coated with "Glidex" coating. This coating is said to produce a hydrophilic surface at least eight times more slippery than an uncoated surface for reducing buckling during advancement, for facilitating crossing of tight strictures and for easing negotiation of difficult curves and advancement through stone-obstructed tracts.
Kurihashi, Opthalmologica, 1993 No. 206, pp. 57-68, teaches recanalization of the lacrimal passage with silicone tubing which consists of three pieces: a thinner central segment joined to two thicker outer segments with sealed distal ends. The tubing extends through the upper and lower canaliculi and the nasolacrimal duct.